Passenger seats provided in aircraft are generally equipped with electrical actuators which allow different movable elements of the seat to be displaced relative to each other.
In order to ensure the safety of passengers during the critical phases of take-off or landing, it is imperative for the seat to be able to have an adequate level of rigidity, which prevents the seat from becoming deformed or becoming disengaged from the remainder of the aircraft in the event of a significant impact. The presence of only the actuators which connect the different elements of the seat is not always sufficient to meet these requirements for strength in the event of an impact.
Therefore, it is known to immobilize specific portions of the seat relative to each other using locks during critical phases of the flight of the aircraft. These locks are constituted, for example, by the movable core of an electromagnet whose winding is carried by a movable portion of the seat and whose movable core can be moved between a retracted position and an extended position, wherein the lock can be engaged in the fixed portion of the seat, thus providing positive mechanical locking of the movement of the two portions of the seat relative to each other.
In arrangements of this type, the movable core of the electromagnet which forms the lock is received in a small catch which is provided in a corresponding portion of the seat.
For the control thereof, the seat is provided with means for controlling the electromagnet so that, before the activation of the actuator which ensures the movement of the two portions relative to each other, the lock is retracted and, conversely, so that the extension of the lock is brought about when the actuator reaches a predetermined position in which the lock is in the catch in order to ensure the activation of the lock.
In practice, it has been found that, taking into account production tolerances of the seat and the actuators, and involuntary movements of the passenger in the seat which may occur, the movement of the lock to the retracted position thereof and/or to the extended position thereof is made difficult, even impossible, owing to the misalignment between the lock and the catch.
In the case of locking, the movement force of the electromagnet, which is relatively small, is often insufficient to disengage or position the lock.